Capturing Pin-Ejection in Drop-Tower Tests of Digger Tooth Systems
Analysis
Objective
A complete LS-DYNA anslysis model was constructed of a drop-tower simulation. Results from this analysis were validated and showed good correlation to videos of the pin-ejection process.
This simulation provided the first true glimpse of the completely transient impact behavior of digger-tooth system. The point (the digging part) is attached to the nose (interior supporting part) by deceptively simple arrangement of steel and rubber pins. The interaction of these pins creates the locking mechnism between the point and the nose. When working as designed - the point or tooth stays "locked" in place during the digging operation (think gigantic buckets and digging systems. When this locking pin ejects the tooth is lost and can cause a bit of a disruption when this massive steel part is ingested by downstream ore processing equipment. The goal of this work was then to learn more about how this pin can eject and use these results to drive the design process toward better locking mechanisms.
Notes: The material models were based on steel and a high-density polyurethane. A simplified rubber model (*Mat_181) was developed based on uniaxial tensile and compressive data. The cast steel material model as implemented using *Mat_24. Contact between the steel and rubber parts was enforced using *Automatic_Surface-to-Surface with Soft=1 due to the large stiffness differences between the two materials.
This video shows the LS-DYNA simulation of the digger tooth being hit by the drop tower hammer. As the point is impacted, the nose compresses and the locking pin mechanism is forced open and the pin is ejected. The material set for the model included high-strength steel along with an elastomeric (rubber) seat component to support the pin. The LS-DYNA results were matched to expermental videos and the correlation was quite amazing.
